RIP: Use message authentication interface

Based on former commit from Pavel Tvrdik

8 files changed, 100 insertions, 34 deletions

diff --git a/lib/mac.h b/lib/mac.h
index 9dba8f89..5fc216fd 100644
--- a/lib/mac.h
+++ b/lib/mac.h
@@ -21,6 +21,7 @@
 #define ALG_SHA256		0x04
 #define ALG_SHA384		0x05
 #define ALG_SHA512		0x06
+#define ALG_HMAC		0x10
 #define ALG_HMAC_MD5		0x11
 #define ALG_HMAC_SHA1		0x12
 #define ALG_HMAC_SHA224		0x13
@@ -34,6 +35,9 @@
 #define HASH_STORAGE		sizeof(struct sha512_context)
 #define MAC_STORAGE		sizeof(struct hmac_context)
 
+/* This value is used by several IETF protocols for padding */
+#define HMAC_MAGIC		htonl(0x878FE1F3)
+
 /* Generic context used by hash functions */
 struct hash_context
 {
diff --git a/lib/string.h b/lib/string.h
index bf0b7cb0..75cb88dd 100644
--- a/lib/string.h
+++ b/lib/string.h
@@ -39,6 +39,16 @@ xstrdup(const char *c)
   return z;
 }
 
+static inline void
+memset32(void *D, u32 val, uint n)
+{
+  u32 *dst = D;
+  uint i;
+
+  for (i = 0; i < n; i++)
+    dst[i] = val;
+}
+
 #define ROUTER_ID_64_LENGTH 23
 
 #endif
diff --git a/nest/password.c b/nest/password.c
index d6e2087f..e4813741 100644
--- a/nest/password.c
+++ b/nest/password.c
@@ -10,6 +10,7 @@
 #include "nest/bird.h"
 #include "nest/password.h"
 #include "lib/string.h"
+#include "lib/mac.h"
 
 struct password_item *last_password_item = NULL;
 
@@ -66,3 +67,17 @@ password_find_by_value(list *l, char *pass, uint size)
   return NULL;
 }
 
+uint
+max_mac_length(list *l)
+{
+  struct password_item *pi;
+  uint val = 0;
+
+  if (!l)
+    return 0;
+
+  WALK_LIST(pi, *l)
+    val = MAX(val, mac_type_length(pi->alg));
+
+  return val;
+}
diff --git a/nest/password.h b/nest/password.h
index 7392389b..f21483c4 100644
--- a/nest/password.h
+++ b/nest/password.h
@@ -34,4 +34,6 @@ static inline int password_verify(struct password_item *p1, char *p2, uint size)
   return !memcmp(buf, p2, size);
 }
 
+uint max_mac_length(list *l);
+
 #endif
diff --git a/proto/rip/config.Y b/proto/rip/config.Y
index e15599e0..4ec45c7a 100644
--- a/proto/rip/config.Y
+++ b/proto/rip/config.Y
@@ -98,15 +98,29 @@ rip_iface_start:
 
 rip_iface_finish:
 {
+  /* Default mode is broadcast for RIPv1, multicast for RIPv2 and RIPng */
+  if (!RIP_IFACE->mode)
+    RIP_IFACE->mode = (rip_cfg_is_v2() && (RIP_IFACE->version == RIP_V1)) ?
+      RIP_IM_BROADCAST : RIP_IM_MULTICAST;
+
   RIP_IFACE->passwords = get_passwords();
 
   if (!RIP_IFACE->auth_type != !RIP_IFACE->passwords)
     log(L_WARN "Authentication and password options should be used together");
 
-  /* Default mode is broadcast for RIPv1, multicast for RIPv2 and RIPng */
-  if (!RIP_IFACE->mode)
-    RIP_IFACE->mode = (rip_cfg_is_v2() && (RIP_IFACE->version == RIP_V1)) ?
-      RIP_IM_BROADCAST : RIP_IM_MULTICAST;
+  if (RIP_IFACE->passwords)
+  {
+    struct password_item *pass;
+    WALK_LIST(pass, *RIP_IFACE->passwords)
+    {
+      if (pass->alg && (RIP_IFACE->auth_type != RIP_AUTH_CRYPTO))
+	cf_error("Password algorithm option requires cryptographic authentication");
+
+      /* Set default crypto algorithm (MD5) */
+      if (!pass->alg && (RIP_IFACE->auth_type == RIP_AUTH_CRYPTO))
+	pass->alg = ALG_MD5;
+    }
+  }
 
   RIP_CFG->min_timeout_time = MIN_(RIP_CFG->min_timeout_time, RIP_IFACE->timeout_time);
   RIP_CFG->max_garbage_time = MAX_(RIP_CFG->max_garbage_time, RIP_IFACE->garbage_time);
diff --git a/proto/rip/packets.c b/proto/rip/packets.c
index 381b4771..468927e6 100644
--- a/proto/rip/packets.c
+++ b/proto/rip/packets.c
@@ -10,7 +10,6 @@
  */
 
 #include "rip.h"
-#include "lib/md5.h"
 #include "lib/mac.h"
 
 
@@ -18,9 +17,7 @@
 #define RIP_CMD_RESPONSE	2	/* responding to request */
 
 #define RIP_BLOCK_LENGTH	20
-
 #define RIP_PASSWD_LENGTH	16
-#define RIP_MD5_LENGTH		16
 
 #define RIP_AF_IPV4		2
 #define RIP_AF_AUTH		0xffff
@@ -73,7 +70,7 @@ struct rip_auth_tail
 {
   u16 must_be_ffff;
   u16 must_be_0001;
-  byte auth_data[];
+  byte auth_data[0];
 };
 
 /* Internal representation of RTE block data */
@@ -221,16 +218,24 @@ rip_fill_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_p
     auth->auth_type = htons(RIP_AUTH_CRYPTO);
     auth->packet_len = htons(*plen);
     auth->key_id = pass->id;
-    auth->auth_len = sizeof(struct rip_auth_tail) + RIP_MD5_LENGTH;
+    auth->auth_len = mac_type_length(pass->alg);
     auth->seq_num = ifa->csn_ready ? htonl(ifa->csn) : 0;
     auth->unused1 = 0;
     auth->unused2 = 0;
     ifa->csn_ready = 1;
 
+    if (pass->alg < ALG_HMAC)
+      auth->auth_len += sizeof(struct rip_auth_tail);
+
     /*
      * Note that RFC 4822 is unclear whether auth_len should cover whole
      * authentication trailer or just auth_data length.
      *
+     * FIXME: We should use just auth_data length by default. Currently we put
+     * the whole auth trailer length in keyed hash case to keep old behavior,
+     * but we put just auth_data length in the new HMAC case. Note that Quagga
+     * has config option for this.
+     *
      * Crypto sequence numbers are increased by sender in rip_update_csn().
      * First CSN should be zero, this is handled by csn_ready.
      */
@@ -238,14 +243,18 @@ rip_fill_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_p
     struct rip_auth_tail *tail = (void *) ((byte *) pkt + *plen);
     tail->must_be_ffff = htons(0xffff);
     tail->must_be_0001 = htons(0x0001);
-    strncpy(tail->auth_data, pass->password, RIP_MD5_LENGTH);
 
-    *plen += sizeof(struct rip_auth_tail) + RIP_MD5_LENGTH;
+    uint auth_len = mac_type_length(pass->alg);
+    *plen += sizeof(struct rip_auth_tail) + auth_len;
 
-    struct hash_context ctx;
-    md5_init(&ctx);
-    md5_update(&ctx, (byte *) pkt, *plen);
-    memcpy(tail->auth_data, md5_final(&ctx), RIP_MD5_LENGTH);
+    /* Append key for keyed hash, append padding for HMAC (RFC 4822 2.5) */
+    if (pass->alg < ALG_HMAC)
+      strncpy(tail->auth_data, pass->password, auth_len);
+    else
+      memset32(tail->auth_data, HMAC_MAGIC, auth_len / 4);
+
+    mac_fill(pass->alg, pass->password, pass->length,
+	     (byte *) pkt, *plen, tail->auth_data);
     return;
 
   default:
@@ -288,13 +297,25 @@ rip_check_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_
       DROP("no suitable password found", auth->key_id);
 
     uint data_len = ntohs(auth->packet_len);
-    uint auth_len = sizeof(struct rip_auth_tail) + RIP_MD5_LENGTH;
+    uint auth_len = mac_type_length(pass->alg);
+    uint auth_len2 = sizeof(struct rip_auth_tail) + auth_len;
 
-    if (data_len + auth_len != *plen)
-      DROP("packet length mismatch", data_len);
+    /*
+     * Ideally, first check should be check for internal consistency:
+     *   (data_len + sizeof(struct rip_auth_tail) + auth->auth_len) != *plen
+     *
+     * Second one should check expected code length:
+     *   auth->auth_len != auth_len
+     *
+     * But as auth->auth_len has two interpretations, we simplify this
+     */
 
-    if ((auth->auth_len != RIP_MD5_LENGTH) && (auth->auth_len != auth_len))
-      DROP("authentication data length mismatch", auth->auth_len);
+    if (data_len + auth_len2 != *plen)
+      DROP("packet length mismatch", *plen);
+
+    /* Warning: two interpretations of auth_len field */
+    if ((auth->auth_len != auth_len) && (auth->auth_len != auth_len2))
+      DROP("wrong authentication length", auth->auth_len);
 
     struct rip_auth_tail *tail = (void *) ((byte *) pkt + data_len);
     if ((tail->must_be_ffff != htons(0xffff)) || (tail->must_be_0001 != htons(0x0001)))
@@ -312,17 +333,18 @@ rip_check_authentication(struct rip_proto *p, struct rip_iface *ifa, struct rip_
       return 0;
     }
 
-    char received[RIP_MD5_LENGTH];
-    memcpy(received, tail->auth_data, RIP_MD5_LENGTH);
-    strncpy(tail->auth_data, pass->password, RIP_MD5_LENGTH);
+    byte *auth_data = alloca(auth_len);
+    memcpy(auth_data, tail->auth_data, auth_len);
 
-    struct hash_context ctx;
-    md5_init(&ctx);
-    md5_update(&ctx, (byte *) pkt, *plen);
-    char *computed = md5_final(&ctx);
+    /* Append key for keyed hash, append padding for HMAC (RFC 4822 2.5) */
+    if (pass->alg < ALG_HMAC)
+      strncpy(tail->auth_data, pass->password, auth_len);
+    else
+      memset32(tail->auth_data, HMAC_MAGIC, auth_len / 4);
 
-    if (memcmp(received, computed, RIP_MD5_LENGTH))
-      DROP("wrong MD5 digest", pass->id);
+    if (!mac_verify(pass->alg, pass->password, pass->length,
+		    (byte *) pkt, *plen, auth_data))
+      DROP("wrong authentication code", pass->id);
 
     *plen = data_len;
     n->csn = rcv_csn;
diff --git a/proto/rip/rip.c b/proto/rip/rip.c
index 37cfa9ac..7b380097 100644
--- a/proto/rip/rip.c
+++ b/proto/rip/rip.c
@@ -590,7 +590,7 @@ rip_iface_update_buffers(struct rip_iface *ifa)
   ifa->tx_plen = tbsize - headers;
 
   if (ifa->cf->auth_type == RIP_AUTH_CRYPTO)
-    ifa->tx_plen -= RIP_AUTH_TAIL_LENGTH;
+    ifa->tx_plen -= RIP_AUTH_TAIL_LENGTH + max_mac_length(ifa->cf->passwords);
 }
 
 static inline void
@@ -702,12 +702,11 @@ rip_reconfigure_iface(struct rip_proto *p, struct rip_iface *ifa, struct rip_ifa
 
   ifa->cf = new;
 
+  rip_iface_update_buffers(ifa);
+
   if (ifa->next_regular > (now + new->update_time))
     ifa->next_regular = now + (random() % new->update_time) + 1;
 
-  if ((new->tx_length != old->tx_length) || (new->rx_buffer != old->rx_buffer))
-    rip_iface_update_buffers(ifa);
-
   if (new->check_link != old->check_link)
     rip_iface_update_state(ifa);
 
diff --git a/proto/rip/rip.h b/proto/rip/rip.h
index f245e612..b24d9536 100644
--- a/proto/rip/rip.h
+++ b/proto/rip/rip.h
@@ -40,7 +40,7 @@
 #define RIP_NG_PORT		521	/* RIPng */
 
 #define RIP_MAX_PKT_LENGTH	532	/* 512 + IP4_HEADER_LENGTH */
-#define RIP_AUTH_TAIL_LENGTH	20	/* 4 + MD5 length */
+#define RIP_AUTH_TAIL_LENGTH	4	/* Without auth_data */
 
 #define RIP_DEFAULT_ECMP_LIMIT	16
 #define RIP_DEFAULT_INFINITY	16